The present invention relates generally to inks. More specifically, the present invention relates to methods of reducing gas in inks, and inks produced from such methods.
Ink jet printing is a non-impact and non-contact printing method in which an electronic signal controls and directs droplets or a stream of ink, that can be deposited on a wide variety of substrates. Current ink jet printing technology involves forcing the ink drops through small nozzles by piezoelectric pressure, thermal ejection, or oscillation, and onto the surface of a material/media. Ink jet printing is extremely versatile in terms of the variety of substrates that can be treated, as well as the print quality and the speed of operation that can be achieved. In addition, ink jet printing is digitally controllable. For these reasons, ink jet methodology has been widely adopted for numerous industrial and personal applications. However, even given the recent rapid advancements in the ink jet printing field, xe2x80x9cprintabilityxe2x80x9d/xe2x80x9crunabilityxe2x80x9d problems remain, that continue to plague the ink jet printer and ink markets.
For instance, it is widely known in the inkjet printing field that dissolved air in inks can cause runability problems for inkjet printers. Dissolved or colloidal air may form small bubbles within feed tubes in the printer print head, disrupting ink flow. Therefore, aqueous inkjet inks are usually subjected to some type of de-aeration process, whereby gases that are either dissolved in true solution, contained in the ink in colloidal form, or chemically adsorbed to particulate surfaces (e.g. pigment particles) are removed. Current methods of degassing inks include either subjecting the ink to a vacuum, or passing helium gas through the ink. As helium gas is less soluble than oxygen or nitrogen gas, these gases are carried out of the ink mixture.
However, even given the usage of such degassing methods, it is recognized that gases such as oxygen and nitrogen are able to diffuse through most polymers, the materials commonly used to store ink jet inks. Eventually, such gases will re-saturate inks stored in such polymeric containers. For instance, as can be seen in FIG. 1, which illustrates a cross section of an exemplary ink cartridge 10 for storing inks 12, even though the ink 12 is contained in a rigid casing 14 which includes a separate flexible bladder 16 that actually contains the ink 12, air may permeate the ink cartridge either from the air space 18 between the rigid casing and the bladder in the cartridge 10, or externally from the cartridge through the rigid casing 14, or the septum 20. The penetration of air is indicated in the Figure by dotted arrows, such as at 22.
Once the level of gases in inkjet inks reaches an appreciable level, runability issues, such as nozzle misfiring, may result. This is particularly apparent for piezo type inkjet print heads that include fine feed channels. Thus, natural diffusion of gases through the container itself may limit ink shelf-life.
The presence of air is particularly problematic in pigmented inks for several reasons. For instance, oxygen is more soluble in the surfactants that are used to stabilize pigment dispersions. Furthermore, the surfactants used can stabilize colloidal gas particles, and pigment dispersions have a large surface area for chemical adsorption of gases to take place.
Other types of ink may also be sensitive to dissolved gasses from the atmosphere. For instance, clear coating inks, glues, varnishes, and resin finishes may contain dissolved air, which, as the applied ink film dries, saturates the drying ink layer to form unsightly air bubbles that remain after the ink layer has dried.
Oxygen sensitivity is also an issue with regard to certain ultra-violet curable inks. Unless care is taken to exclude oxygen during the curing step (exposure to ultraviolet (UV) radiation) oxygen may inhibit the photocuring reaction, leading to tackiness of the final coating.
Therefore, there is a need in the art for inks that do not allow for the gases of air to build up in the ink mixture. There is also a need for methods of degassing inks prior to use. Finally, there is also a need for such inks and methods for use with inks, specifically for inkjet printing on textiles, and for inks utilizing pigments as coloring agents, for inks that are cured using ultraviolet light, and for inks that dry to give a clear finish, as well as any other oxygen or air sensitive ink.
A method for degassing ink includes the addition of at least one enzyme to ink containing a donor substrate, with the enzyme capable of catalyzing the production of a reaction product that is acceptable to an ink formulation, by using a donor substrate contained in the ink upon exposure to a gaseous acceptor substrate.
Alternatively, a method for degassing ink includes the addition of at least two enzymes to ink containing a donor substrate specific to each enzyme, wherein one of the enzymes catalyzes a chemical reaction to produce a first reaction product upon exposure to a gaseous acceptor substrate, and another enzyme subsequently catalyzes a reaction to convert the first reaction product into a second reaction product that is acceptable in an ink system.
Still further, another alternative method for degassing ink includes the addition of at least two enzymes to ink containing a donor substrate specific to each enzyme, wherein one of the enzymes catalyzes a chemical reaction to produce hydrogen peroxide upon exposure to a gaseous acceptor substrate, and another enzyme subsequently catalyzes a reaction to convert the hydrogen peroxide into water.
As another aspect of the invention an ink composition includes at least one enzyme, and a donor substrate specific to the enzyme, with the enzyme being capable of catalyzing the production of a reaction product that is acceptable to the ink formulation, by using the donor substrate contained in the ink, upon exposure to a gaseous acceptor substrate.
A further ink composition includes at least two enzymes and a donor substrate specific to each enzyme, wherein one of the enzymes is capable of catalyzing a chemical reaction to produce a first reaction product upon exposure to a gaseous acceptor substrate, and another enzyme is capable of subsequently catalyzing a reaction to convert the first reaction product into a second reaction product that is acceptable to the ink.
Still a further ink composition includes at least two enzymes and a donor substrate specific to each enzyme, wherein one of the enzymes is capable of catalyzing a chemical reaction to produce hydrogen peroxide upon exposure to a gaseous acceptor substrate, and another enzyme is capable of subsequently catalyzing a reaction to convert the hydrogen peroxide into water.